In numerous industrial situations, there is a need to form a seal between two concentric round structures, for instance between the exterior of a pipe and the throughbore of a housing in which the pipe is disposed, or between two coaxially related pipes one of which is partially surrounded by the other so that there is an annular, cylindrical space defined between them. Sometimes all or most of a sealing device for forming such a seal is run into the annulus with one of the pipes, and then set after the desired relative longitudinal positioning of the pipes has been achieved. Other times all or most of the sealing device is run into the annulus, separately, after the pipes are in place, and then set.
Conventional uses of some conventional sealing devices which are made to be used in forming such annular seals often present at least some of the following problems: that the seal elements are destroyed by the pressures to which they are subjected during make-up or use; that metal seal rings cut-into the surfaces against which they seat; that running and/or retrieval is difficult because of the dragging effect of some element or elements of the sealing device against at least one of the parts with which it is to seal; that in order to test whether the sealing device has been satisfactorily set it is necessary to place more of a compression load upon some other item of equipment located in the inter-conduit annulus than that item of equipment should prudently be called-upon to bear; that the sealing device has a narrow operating temperature range due to differential expansion/contraction between one or more of the sealing elements and one or both of the pipes or the like; that one or both of the pipes or the like must be provided with a bowl or shoulder where the pipe or the like has an abrupt increase or decrease in internal or external diameter; and that the sealing device is difficult or impossible to correctly install in some instances because the two pipes are not precisely concentrically disposed, or one or both are not precisely circular, or one or both of the pipe surfaces is or are rough in places.
The sealing device of the present invention was devised to overcome these drawbacks.